Plasma free norepinephrine and epinephrine concentrations following diazepam-ketamine induction in patients undergoing cardiac surgery.

Ketamine causes cardiovascular stimulation, presumably, by increasing central sympathetic activity. This study was undertaken to find out if diazepam in appropriate doses could abolish or moderate the central sympathetic and cardiovascular stimulation following ketamine in patients undergoing cardiac surgery. Twelve patients, scheduled for valvular replacement (8) and direct aortocoronary bypass graft operations (4) were studied. After premedication with diazepam 0.15 mg/kg orally and morphine sulphate 0.15 mg/kg i.m., they were induced with diazepam 0.3 mg/kg i.v., followed 10 min later by ketamine 2 mg/kg i.v. Direct arterial pressure by a strain gauge from the radial artery and heart rate by EKG were continuously recorded. Plasma free norepinephrine, measured by Vendsalu's method, in the arterial blood was 0.39 +/- 0.03 ng/ml prior to induction, 0.39 +/- 0.03 ng/ml 10 min after diazepam and 0.42 +/- 0.05 ng/ml (P greater than 0.05) 5 min after ketamine administration. Plasma free epinephrine concentrations were 0.10 +/- 0.04 ng/ml prior to induction, 0.06 +/- 0.03 ng/ml (P less than 0.05) 10 min after diazepam and 0.01 +/- 0.003 ng/ml (P less than 0.05) 5 min after ketamine. Heart rate and systolic pressure did not change significantly throughout the study period. Diastolic pressures were elevated significantly (P less than 0.05) 5 min after ketamine administration, amounting to a 12% increase over baseline. Diazepam-ketamine induction in cardiac surgical patients did not result in clinically significant central sympathetic or cardiovascular stimulation.